1. Field of the Invention
The present invention relates to thermally insulated shipping container liners, and, more particularly, to container liners that are inflatable. More specifically, the present invention relates to an envelope composed of multiple layers of a polymeric material that, upon inflation, form baffled layers configured as a shipping container liner.
2. Description of the Prior Art
In the transportation and distribution of products, both the product and the package define the xe2x80x9cshipping environmentxe2x80x9d. While the corrugated fiberboard boxes, steel drums, wooden crates, and pallets have not changed significantly over the past 80 years, the shipping requirements of the products have changed with each new generation of both product and shipping technology. As a result, packaging materials have improved to meet the demands of the new technology.
Refrigerated transportation at one time meant a horse-drawn wagon packed with ice and straw. Super-cooled gases and microprocessor-controlled motors have replaced the earlier, primitive refrigeration techniques. Reliable, temperature-controlled, surface transportation is now available to and from almost anywhere in the world. Trucks and ocean container shipping utilize positive, mechanical refrigeration systems to retard spoilage in transit.
Such surface transportation is relatively slow, and the shipped goods must have a correspondingly long shelf life. However, many temperature-sensitive products, such as perishable foodstuffs, are time-sensitive as well. Successful long-distance shipping is only feasible where transportation time can be minimized.
Servicing a worldwide food market required yet another technological development C the generous cargo holds of newer, wide-body passenger jet aircraft in the late 1960""s and early 70""s. The drop in airfreight rates heralded by these new jets for the first time permitted the cost-effective transportation of perishable, medium-value commodities such as meat, seafood, and fresh produce.
Traditionally, such perishable foodstuffs, as well as pharmaceuticals, are cooled prior to shipment, then placed within a thermal insulating material, and shipped with only a modicum of ice or refrigerant to absorb the heat that flows through the insulation. For many years, molded expanded polystyrene (xe2x80x9cEPSxe2x80x9d) containers have been the thermal insulating material of choice. The perishable goods are placed within the EPS containers, which are then in turn placed within small, corrugated shipping boxes.
EPS containers have been widely used since the lowered airfreight rates first made this form of shipment economically practical. While providing satisfactory insulation qualities as well as being light in weight, EPS also presents several negative characteristics to the shipping industry. EPS is an xe2x80x9cexpanded,xe2x80x9d non-compressible material, and consists of a very large number of small air bubbles formed in a polystyrene plastic matrix. EPS""s poor volume efficiency increases shipment costs when transporting the empty containers to the location of their use, as well as causing increased warehousing costs when stored in inventory prior to use.
While providing reasonable protection from shock impacts during transit, EPS has poor resistance to the application of puncture and shear loading. EPS easily fractures, requiring the use of an additional plastic liner bag when shipping products with a liquid component, such as ice-chilled, fresh seafood. The lack of such an additional plastic liner risks liquid leakage from the EPS container during shipment, and the resultant expensive damage to aircraft cargo holds or other corrosion-sensitive shipping environments.
In an effort to avoid EPS and its negative characteristics, a number of shippers have attempted to make use of metallized, radiant barrier bags. Relying on the property of shiny, metallized coatings to reflectively radiate heat energy, such products have found only marginal success as insulated packaging. Although reducing warehousing and breakage expenses, as well as enjoying lower manufacturing costs, many shippers have determined that such radiant bags do not control temperatures over a sufficiently long period of time.
Ideally, it would be desirable to provide an insulative system having a reliable thermal performance over extended time periods (at least 48 hours), which is leak proof, can be shipped and stored in a manner requiring less space than EPS, and that is fabricated out of materials and in a manner that remains cost-competitive with the EPS insulated box product.
Griffith, et al., in U.S. Pat. No. 5,270,092, suggests an inflatable insulating alternative. Fabrication of an outer envelope is suggested to be out of a multi-layer polymeric material, with multiple layers of baffles contained within the envelope. One or more of the baffle surfaces are covered by a low emissivity surface, to further suppress heat transfer in the form of infrared radiation.
Despite the promise of the Griffith, et al., baffled envelopes, that structure has resisted prior efforts for a commercially practical method of fabrication. Present commercial insulative materials, such as expanded polystyrene (xe2x80x9cEPSxe2x80x9d), have continued to maintain a manufacturing cost advantage. A need thus exists for an inflatable, baffled envelope structure that can be inexpensively manufactured, yet provide insulation performance that is equal to or in excess of such presently used materials as EPS.
It is an object of the present invention to provide an insulated liner for cargo shipping containers having thermal insulation performance exceeding that obtained by EPS insulating containers. In this regard, the multiple baffles defining the container walls provide individual air chambers, each having a metallized surface to address the three modes of heat transfer: conduction, convection, and radiation in a manner that minimizes such transfer. As a result, testing under the ASTM C-518 standards has shown an 18% performance improvement by the baffled construction of the present invention over that provided by the same wall thickness of EPS.
A further object of the present invention is to reduce costs previously associated with the use of EPS. One such cost reduction is achieved as a result of the greater thermal efficiency previously discussed. The enhanced thermal insulation characteristic obtained under the present baffled liner enables extended shipping times without compromising the quality of the thermally-sensitive cargo.
Additional savings is obtained through reduced storage and transport costs. When stored, the present baffled container is in a collapsed, un-inflated state that occupies only {fraction (1/20)}th the space required by the alternative, molded EPS containers. Not only does this volume reduction result in saved warehouse space, the transport of the in-inflated liner to the shipping site is considerably more efficient as a result of its reduced, per unit shipping volume.
A still further object of the present invention is to provide a baffled container liner that is virtually leak-proof in terms of container integrity. Constructed from multiple layers into a flat, easily stored envelope, when used, the envelope inflates into a closed-end container preventing liquid leakage from within. During transit, such liquid might originate from the cargo itself, or from the refrigerant, which is frequently ice. Such liquid is unwelcome to cargo air carriers, as it has the potential to be damaging to the airplane structure and cleanup can be quite expensive and time-consuming to accomplish.
A further object of the invention is obtained through its baffled construction. Upon inflation, the baffled layers of the flat envelope become substantially rigid, thus creating the container walls. These inflated walls, in addition to forming the container structure, also provide a degree of protective cushioning for sensitive perishables carried within.
The disposal problems associated with EPS are well known. In addition to creating a large volume of refuse, it is slow to breakdown, persisting as a landfill problem over many years. A further object obtained by the present invention is a reduction in the disposal profile for insulating liners. In addition to physically occupying less space, the polyolefin films used deteriorate much more rapidly in landfills than does EPS.
A still further object of the present invention is to provide a surface upon which to place customized graphics, using multiple colors. The polyolefin films utilized in the present invention provide a surface that is substantially equivalent to the plastic carriers used to create modern billboard displays. The present invention enables use of such films having pre-applied graphical images to form the outer surface of the insulating container liner. The film bearing the image(s) is precisely positioned during construction of the liner to enable creation of the inflated container having the desired graphical images.
Some further objects and advantages of the present invention shall become apparent from the ensuing description and as illustrated in the accompanying drawings.